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Biosphere and Surface of the Earth

Makin' The Soil

The process of soil formation happens in many ways. Here are five of the most important factors involved in soil formation. There are others, but these are the biggies.

(1) It can be created because of the shape of the landscape. That shape is called the topography. When you have mountains, the sides of the mountains are said to have a slope. When you have a slope and it rains, there will be drainage. The runoff carries away small rocks and minerals. This runoff winds up in valleys or in the ocean. It slowly builds up and the small pieces make soil.

(2) There are climatic effects that create soil. Moisture and rain combine with the temperature to do amazing things to rocks. We just explained that when it rains you have runoff and erosion. Those physical activities break down the rocks and hard surfaces. Temperature plays a role when you move below and above the freezing point. When water freezes, it expands. Rocks and soil that hold water can be cracked when the water freezes and expands. They pop open with a cracking sound!

(3) What's in the soil is dependent on geologic factors. The type of soil under your feet is dependent on the bedrock deep below the surface. As the bedrock breaks down, smaller pieces move to the surface and mix with the existing soil.

(4) In the same way that there are large geologic factors, chronological factors play an important part in the process. Chronological means time. You need time to make soil. That's it. Sediment can move around quickly but it takes a long time to break down bedrock. We can't just sit and watch this process happen. We have to study it over many years. Also, if we pollute our soil we can't renew it in our lifetime. It takes hundreds to thousands of years.

(5) Soil is also created by biological factors. You'll find that soil is half minerals/rocks and half air/water. All sorts of biological things are happening in the air/water space. The organic material is most important. There are tiny living organisms (like bacteria) that break down organic stuff. The "stuff" could be dead leaves or dead animals. The organic stuff is called humus. There are also roots and tunneling creatures that work like the microbes. They turn the soil around and move it. They churn the pieces of soil.

Next page on the biosphere.
- Overview
- Ecology
- Ecosystems
- Food Chains
- Populations
- Land Biomes
- Erosion
- Deep Erosion
- Weathering
- Soils
> Soil Formation
- Natural Resources
- Energy Resources
- Recycling


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Study of Mangrove Peat Development (USGS Video)
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Biosphere of Earth Quiz

Land Biome Panoramas

Useful Reference Materials (Soil Formation):
Wikipedia (Pedogenesis):
Encyclopædia Britannica (Soils in Ecosystems):

- Geography4Kids: Natural Resources
- Chem4Kids: Solids
- Chem4Kids: Biochemistry
- Chem4Kids: Environmental Chemistry
- Biology4Kids: Plants
- Biology4Kids: Kingdoms
- Biology4Kids: Microbes
- Biology4Kids: Invertebrates
- Biology4Kids: Vertebrates
- Cosmos4Kids: Earth
- Cosmos4Kids: Sun
- Physics4Kids: Alternating Current

- NASA: Kennedy Space Center
- NASA: Goddard Spaceflight Center

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